"Plasma estradiol and testosterone levels were significantly elevated in serious leisure male cyclists, a finding not previously reported in any type of male athlete," said Leah FitzGerald, an assistant professor at the UCLA School of Nursing, and principal investigator and senior author of the study.

Estradiol is a form of estrogen and, in males, is produced as an active metabolic product of testosterone. Possible conditions associated with elevated estrogen in males include gynecomastia, a condition that may result in the loss of pubic hair and enlarged breast tissue.

"Plasma estradiol concentrations were more than two times higher in the cyclists than in the triathletes and recreational athletes, and total testosterone levels were about 50% higher in cyclists than in the recreational athletes," said researchers, in a statement.

Women who spend a lot of time in the saddle can experience decreased genital sensation, a study by Yale found.

Published in the Journal of Sexual Medicine, the paper found women whose handlebars are lower than the saddle were especially at risk, as the position results in increased pressure on the nerves and blood vessels surrounding the genitalia.

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Commenting on the results of her study of male sex hormones, FitzGerald said: "Although preliminary, these findings warrant further investigation to determine if specific types of exercise may be associated with altered sex-hormone levels in men that could affect general health and reproductive well-being."

Another interesting study finding related to to the use of chamois cream.

Some cyclists applied it to their perineum area to help prevent chaffing and bacterial infections related to bicycle saddle sores.

However, many commercial creams contain a variety of ingredients, including lubricants, polymers and oils, and some also contain parabens, which are anti-microbial preservatives and weak estrogen agonists.

In the study, 48.5% of cyclists — compared with 10% of triathletes — reported using a paraben-containing chamois cream.

The study found an association between an increase in estrogen levels and increasing years of chamois cream use, particularly for male cyclists using the cream for more than four years.

At this time, however, no direct cause and effect has been found, the researchers said.